NBC News reporter Katy Tur tweeted that members of the media were told they couldn't leave the designated press area, often described as a pen, "while Trump is in the room." She added that this restriction is "now official policy that the secret service is enforcing."

The Secret Service began providing Trump and fellow Republican candidate Dr. Ben Carson with protection earlier this month at their request and following approval from the Department of Homeland Security. No other candidates have such protection, except Democratic frontrunner Hillary Clinton, who as a former first lady has Secret Service protection for life.

But the Trump campaign has been particularly aggressive in calling on the Secret Service -- or citing the agency's concerns -- to enforce press restrictions. Last week, Trump campaign manager Corey Lewandowski threatened to "blacklist" CNN reporter Noah Gray for leaving the pen to cover a protester at a Massachusetts rally. Though the Trump campaign claimed it reacted in response to Secret Service concerns about reporters moving into the crowd, an agent told Gray that wasn't the case.

What happens off stage at Trump events is particularly newsworthy these days as events grow increasingly tense and, at times, violent. On Saturday in Birmingham, Alabama, several white supporters apparently punched and kicked a Black Lives Matter activist who interrupted a rally, a violent response Trump condoned the next morning on Fox News.

The enforcement of restrictions at events has been inconsistent, according to one reporter who is not authorized to speak on the record. On Monday, a Secret Service agent kept reporters in the "pen" in Columbus, Ohio, the reporter said, but it was a Trump campaign staffer enforcing the restriction on Tuesday night in Myrtle Beach.

A Secret Service spokesman did not specifically address the restrictions at the Trump rallies, but broadly described the agency's role at campaign events in a statement to The Huffington Post.

"It is not a function of the Secret Service to prevent or limit the press from conducting interviews at events attended by our protectees," he said. The spokesman continued:

However, those with press credentials are always segregated from the general public for logistical and security reasons. Members of the press are free to attend events as general public with the same access as general public. It is their choice as to whether they will attend as part of the media pool.

If they choose to attend as part of the credentialed media pool, they must adhere to those logistical rules that govern the pool’s movements. If they choose to attend as a member of the general public, they have the right to intersperse with the other members of the crowd however they see fit.

Credentialed members of the press are also free to interview event attendees outside of established security perimeters or inside those perimeters once our security protocols have been lifted.

The Trump campaign did not respond to a request for comment.

Other campaigns have faced scrutiny over access this cycle, including the Clinton team after aides corralled reporters during a July 4 parade.

Also, there may be some growing pains when Secret Service gets involved given that events become more complicated logistically. The agency needs to conduct security sweeps hours beforehand, screen journalists and members of the public, and possibly cordon off certain areas.

But the Trump campaign's recent restrictions inside rallies follow its unusual tendency to prevent some reporters from attending events altogether.

On Thursday, the campaign barred a BuzzFeed reporter from attending an Iowa event, even though he'd already gone through Secret Service screening. The campaign wouldn't let the reporter enter with the general public, either. In recent months, the Trump campaign has denied credentials to reporters from BuzzFeed, Fusion, The Des Moines Register, and The Huffington Post, which has shifted much of its coverage of Trump to the Entertainment section.

Trump has also routinely bashed the media throughout his candidacy and this week pushed back against the press when confronted with facts that challenged his claims about events surrounding the 9/11 attacks. On Tuesday, Lewandowski even claimed journalists were suppressing evidence that would support Trump's assertion Saturday that "thousands and thousands" of people in Jersey City, New Jersey, cheered as the twin towers fell.